The present invention relates to a Schottky gate field effect transistor (hereinafter referred to as MESFET) formed on a compound semiconductor substrate, such as a GaAs substrate.
In general, GaAs MESFET comprises GaAs a channel formed by doping doner ions such as Si ions in a surface layer of a GaAs substrate and performing heat treatment, a Schottky gate electrode formed on the channel, and a source region and a drain region adjacent the channel, a source electrode and a drain electrode formed over the source region and the drain region and on the respective sides of the Schottky gate electrode. To improve the K value (its definition being given hereinbelow) and gm (mutual conductance) in a conventional MESFET, ion implantation is performed with a low energy and a high-concentration to form a channel, or as described in the Extended Abstract of the 16th (1984 International) Conference on Solid State Devices and Materials, Kobe, 1984, pp. 395-398, ions, such as C ions and O ions, which will become carrier killers are implanted at a high energy to kill carriers at a deep part of the channel thereby forming a channel having a steep profile.
The MESFET of these structures can have improved K value and mutual conductance gm, but there is an attendant effect that the dielectric breakdown voltage (withstand voltage) is degraded.